The invention is directed to a process for the recovery of pure nicotinamide from crude nicotinamide by recrystallization in alkanol. The invention particularly is directed to a process for freeing the nicotinamide from the impurities nicotinic acid and salts of nicotinic acid, e.g. sodium nicotinate, ammonium nicotinate and potassium nicotinate.
Nicotinamide is generally produced by hydrolysis of nicotinonitrile in acid or alkaline medium or by reaction of nicotinic acid with ammonia. The crude nicotinamide obtained in this process of production contains impurities, especially nicotinic acid (generally about 0.3 to 5.0%) and salts of nicotinic acid (generally about 1.5 to 2.5%). These impurities create problems in the further use of the nicotinamide, namely in the pharmaceutical area, especially if their amount exceeds 0.1%.
It is known to purify crude nicotinamide with the help of ion exchangers. The nicotinamide for this purpose is led in solution in water or polar organic solvent, in a given case at an elevated temperature up to 50.degree. C. over an anion exchanger and thereby the nicotinate ions are bound (British Pat. No. 879551 and Finkelstein U.S. Pat. No. 3,678,060. The entire disclosures of the British patent and Finkelstein are hereby incorporated by reference and relied upon). These processes require considerable expense and give poor yields if there should be obtained nicotinamide sufficiently purified from nicotinate ions. Besides they are only suited for the cases where there is not needed a separation of the cations.
It is also known to purify crude nicotinamide by recrystallization. In this case there are used as solvents acetone (Duesel, U.S. Pat. No. 2,471,518), propanol-2 or butyl acetate in the presence of decolorizing carbon (German Pat. No. 828,247), ethyl acetate (Krewson, J. Amer. Chem. Soc. Vol. 65 pages 2256-2257 (1943)), ethanol in the presence of activated carbon (Galat, J. Amer. Chem. Soc. Vol. 70 page 3945 (1948)), dioxane or petroleum ether (Pike U.S. Pat. No. 2,412,749) or benzene (Danish Pat. No. 87228).
A disadvantage of these processes is that for the production of a sufficiently pure nicotinamide multiple recrystallization is required and only a moderate yield of pure nicotinamide is produced.